An embodiment of the present invention relates to a repair circuit including a repair controller for reducing current dissipation.
Semiconductor memories are additionally equipped with spare memory cells (hereinafter referred to as “redundancy cells” or “redundant cells”) for replacing defective memory cells, which are incapable of operating in normal conditions due to defects in memory cell arrays, for the purpose of enhancing product yields thereof. Establishing the number of the redundant cells highly affects yields of semiconductor memories. For instance, a semiconductor memory chip having redundant cells larger than defective cells is disadvantageous to integration density because the redundant cells necessarily cause the chip size to increase. To the contrary, semiconductor memory chips having redundant cells smaller than defective cells are abolished as inferior products, which degrade the product yield. Therefore, evaluating the number of redundant cells in a reasonable degree is important in designing a semiconductor memory.
In a semiconductor memory having a sufficient number of redundant cells, the redundant cells are partly unused for replacing defective cells. Although that, since the redundant cells unused for replacing defective cells are put into a control operation of repair, there would be unnecessary current dissipation. Such current dissipation induces power noise to cause malfunctions in the semiconductor memory.